Gas turbine fuel system comprising fuel oil distribution control system, fuel oil purge system, purging air supply system and fuel nozzle wash system

ABSTRACT

A plurality of fuel nozzles X 1  and X 2  in combustor X are supplied with fuel gas from a fuel gas system and fuel oil from a fuel oil system, respectively. Gas turbine operation is performed with fuel being changed over to either gas or oil. Fuel oil distribution control system A controls oil flowing into a plurality of fuel pipings. When oil is changed over to gas, fuel oil purge system B is supplied with air of an appropriate temperature and pressure from purging air supply system C. This air flows into fuel oil pipings and nozzles X 2  for purging residual oil therein. Fuel nozzle wash system D is supplied with water by-passing from a wash water tank for compressor washing. This water flows through nozzles X 2  for washing thereof.

This is a Divisional Application of prior U.S. patent application Ser.No. 09/781,420, filed Feb. 13, 2001, (currently pending) which is aDivisional Application of prior U.S. patent application Ser. No.09/305,459, filed May 6, 1999 (now U.S. Pat. No. 6,216,439).

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to a gas turbine fuel system andmore specifically to a gas turbine fuel system comprising a fuel oildistribution control system, a fuel oil purge system, a purging airsupply system and a fuel nozzle wash system in which, fuel oildistribution is controlled to be done uniformly to a plurality of fuelnozzles with enhanced reliability of fuel distribution, and residual oilin fuel pipings and nozzles, when gas turbine operation is changed overto gas fuel from oil fuel, is purged effectively so that a load changecaused by burning of the residual oil at the time of purging isprevented.

2. Description of the Prior Art

FIG. 9 is a block diagram-of an entire gas turbine fuel systemcomprising therein a fuel oil supply system, a fuel oil purge system, apurging air supply system and a compressor outlet wash system in theprior art. In FIG. 9, a combustor X comprises therein a plurality, about20 pieces for example, of fuel nozzles X₁, X₂ disposed along an innerperiphery thereof. The fuel nozzles X₁ are supplied with fuel gas from afuel gas supply system and the fuel nozzles X₂ are supplied with fueloil from a fuel oil supply system G. The gas and oil are changed over toeither one thereof to be supplied into the combustor X for combustion.The fuel oil supply system G, as mentioned, is a system for supplyingtherethrough fuel oil and a fuel oil purge system H is a system forpurging oil remaining in the piping system or fuel nozzles when the fuelis changed over to gas from oil. A purging air supply system J suppliestherethrough a purging air into the fuel oil purge system H. Acompressor outlet wash system K is a system for injecting water into acompressor outlet for washing this compressor outlet which communicateswith the combustor. Description will be made further on each of theabove systems.

The fuel oil supply system G will be described first. In the gasturbine, a stable combustion is required for a wide range of fuel flowrates from ignition to power output. Especially, in the low fuel flowrate range at the time of ignition etc., there is only a smalldifferential pressure of the fuel nozzles in the combustor, whichresults in an unstable combustion. In recent gas turbines there areprovided a large number of fuel nozzles, of about 20 pieces, and therearises an imbalance in the fuel flow rate due to the influence of thehead difference between upper ones and lower ones of the fuel nozzles,which are vertically disposed. For this reason, a flow divider isprovided so that fuel is divided to be supplied uniformly to each of thefuel nozzles. But this flow divider is not necessarily of a sufficientreliability, and troubles in the fuel system are thereby often caused.

FIG. 10 is a diagrammatic view of the fuel oil supply system G in theprior art. In FIG. 10, fuel oil is flow rate controlled by a flowcontrol valve 11 to then flow through a piping 12 and enter a flowdivider 80 to be divided there to flow through a plurality of pipings 82of about 20 pieces and to be supplied into each of the fuel nozzles X₂of the combustor X. The gas turbine fuel nozzles X₂ are disposed inabout 20 pieces along a circumference and there is a head difference ofabout 4 m between the nozzles of upper positions and those of lowerpositions. This head difference produces an imbalance in the fuel flowrate, especially in the low fuel flow rate range at the time ofignition. For this reason, the flow divider 80 is provided, but thisflow divider 80 is constructed such that a spiral shaft is disposed in acylindrical body, and while this shaft is rotated, fuel oil flows intothe cylindrical body to be divided to flow through each of the pluralityof pipings 82 uniformly. A motor 81 is operated only during theoperation start time for ensuring a smooth start of rotation of the flowdivider 80.

FIG. 11 is a view showing a relation between load transition (fuel flowrate) and system differential pressure in the prior art gas turbine,wherein as load increases, fuel flow rate increases from gas turbineignition time t₀ to rated speed (no load) arrival time t₁, and furtherto time t₂ when the system differential pressure, including nozzledifferential pressure, comes to a necessary nozzle differential pressureV₁. That is, during the time T from t₀ to t₂, the system differentialpressure does not reach the necessary nozzle differential pressure V₁,but reaches V₂ at time t₂ to increase more thereafter. Accordingly, thenozzle differential pressure is low during the time shown by T, and ifthere is a head difference between the plurality of fuel nozzles, thereoccurs an imbalance of fuel flow rates between each of the fuel nozzles,hence the flow divider 80 is operated so that the imbalance of the fueloil between each of the fuel nozzles may be eliminated. But this flowdivider 80 has a very small gap between the inner rotational body andthe stationary portion for its function, and this makes control offoreign matter difficult and has often been a cause of trouble in thefuel system.

Next, the fuel oil purge system H will be described. FIG. 12 is adiagrammatic view of the fuel oil purge system in the prior art at thetime when the gas turbine fuel is changed over. In FIG. 12, numeral 1designates a flow control valve in a fuel gas system, numeral 2designates a piping therefor, numeral 3 designates a fuel gasdistributor, which distributes the fuel gas to the plurality of fuelnozzles X₁ and numeral 4 designates a plurality of pipings, which supplytherethrough the fuel gas from the fuel gas distributor 3 to therespective fuel nozzles X₁.

Numeral 11 designates a flow control valve in a fuel oil system, numeral12 designates a piping therefor, numeral 13 designates a header, whichdistributes the fuel oil from the piping 12 to the plurality of fuelnozzles X₂ and numeral 14 designates a plurality of pipings, which areconnected to the header 13 and supply therethrough the fuel oildistributed by the header 13 to the respective fuel nozzles X₂. Numeral26 designates a purging air system piping, numeral 25 designates anopening/closing valve, numeral 23 designates a drain valve piping andnumeral 24 designates an opening/closing valve therefor. Combustor Xcomprises therein the fuel nozzles X₁, X₂.

In the mentioned system so constructed, while the operation is done withthe fuel oil being burned, the fuel oil flowing through the flow controlvalve 11 and the piping 12 is distributed by the header 13 to flowthrough the plurality of pipings 14 to the respective fuel nozzles X₂.The fuel oil so distributed is injected into the combustor X from thefuel nozzles X₂ for combustion.

When the operation is done with the fuel being changed over to gas fromoil, the flow control valve 11 is closed and the fuel gas is led insteadinto the piping 2 to be supplied to the fuel nozzles X₁ through the fuelgas distributor 3 and the piping 4. In this case, the previous fuel oilremains as it is in the pipings 12, 14, and this fuel oil, if leftthere, is carbonized to stick there, with a fear of causing blockage ofthe pipings and nozzles. Hence, it is necessary to remove such residualoil when the fuel is changed over to gas.

Thus, the opening/closing valve 25 is opened so that purging air 40 isled into the piping 12 from the purging air system piping 26. Thepurging air 40 enters the header 13 through the piping 12 to then flowthrough the pipings 14 to the fuel nozzles X₂ to be blown into thecombustor X. Thereby, the fuel oil which remains in the piping 12,header 13, pipings 14 and fuel nozzles X₂ is all discharged into thecombustor X. This purging of the residual oil is done while theoperation is continued with the fuel gas being supplied and burned inthe combustor X. But there is a considerable quantity of such residualoil itself in the piping 12, header 13, pipings 14 and fuel nozzles X₂,and also there are provided a large number of the fuel nozzles X₂, andthe same number of the pipings 14 connected to the respective fuelnozzles X₂. Accordingly, if the residual oil in these portions is alldischarged into the combustor X and the operation is continued with thefuel gas so changed over, then the fuel oil so discharged into thecombustor X burns so that the fuel increases beyond a planned supplyvalue, which elevates the combustion temperature to cause a large loadchange. Hence, realization of a fuel oil purge system which does notcause such a load change has long been desired.

Next, the purging air supply system J will be described. In the recentgas turbine, there is realized an operation system wherein fuel ischanged over to gas from oil, as mentioned above. This operation systemcomprises both the fuel oil system, and fuel gas system and it isnecessary to purge fuel pipings and nozzles on the side not used.Especially in the fuel oil system, oil remains in the pipings and, ifleft as it is, is carbonized to stick there, and there is a fear ofblockage of the pipings and nozzles.

FIG. 13 is a diagrammatic view of the purging air supply system J in theprior art gas turbine. In FIG. 13, numeral 110 designates a gas turbine,numeral 42 designates piping for taking out therethrough outlet air ofan air compressor and numeral 90 designates an air cooler, whichcomprises therein a multiplicity of tubes communicating with the piping42. Numeral 91 designates a motor for rotating a fan 92 to therebysupply air to the air cooler 90 and numeral 43 designates pipingconnecting to outlet of the air cooler 90. Numeral 93 also designatespiping, which diverges from the piping 42 for obtaining air of the purgesystem, and numeral 94 designates a cooler using water 95 for coolingthe air from the piping 93. Numeral 96 designates piping connected to anoutlet of the cooler 94, numeral 97 designates a drain separator,numeral 98 designates piping connected to outlet of the drain separator97, numeral 53 designates a pressure elevation compressor and numeral 99designates piping connected to an outlet of the pressure elevationcompressor 53. Numeral 100 designates a cooler using water 101 forcooling the air which has been heated to a high temperature by pressureelevation at the pressure elevation compressor 53 to an appropriatetemperature as fuel nozzle purging air. Numeral 48 designates piping forsupplying therethrough the air which has been cooled to the appropriatetemperature as the purging air at the cooler 100.

In the mentioned system so constructed, the air of the compressor outletof about 400° C. is cooled at the air cooler 90 to about 200° C. to 250°C. to be supplied into the gas turbine 110 as rotor cooling air throughthe piping 43. A portion of the air of the compressor outlet divergesfrom the piping 42 and is led into the cooler 94 through the piping 93to be cooled to about 130° C. to then be sent to an inlet of thepressure elevation compressor 53. This air is removed of drainage by thedrain separator 97 disposed between the pipings 96 and 98. Then the airis compressed to a predetermined pressure at the pressure elevationcompressor 53 and its temperature is also elevated to about 200° C. Thisair of about 200° C. is led into the cooler 100 through the piping 99 tobe cooled to about 150° C., which is appropriate for purging, and isthen supplied to each of the fuel systems through the piping 48 as thepurging air.

Thus, in the purging air supply system, as the inlet temperature of thepressure elevation compressor 53 becomes high there is provided thecooler 94 for cooling the compressor outlet air of about 400° C. toabout 100° C. to 130° C. Also, as the air, when compressed at thepressure elevation compressor 53, is heated to about 200° C., it iscooled again at the cooler 100 to about 150° C. In this kind of system,therefore, there are needed the coolers 94, 100 or the like, whichrequires large facilities and space therefor. Hence, it has been neededto improve these shortcomings and to attain cost reduction.

Next, the compressor outlet washing system K will be described. FIG. 14is, a diagrammatic view of the compressor outlet wash system in theprior art. In FIG. 14, letter X designates a combustor, numeral 112designates a compressor outlet and numeral 113 designates a manifold fordistributing wash water in an annular form, as described later. Numeral114 designates a plurality of wash nozzles, which are provided along aperiphery of the manifold 113 for injecting therefrom wash water intothe compressor outlet 112. Numeral 11 designates a flow control valvefor fuel oil, numeral 12 designates a piping and numeral 13 designates aheader for distributing fuel into a plurality of fuel supply pipings 14.Fuel oil is supplied from the respective fuel supply pipings 14 to aplurality of fuel nozzles X₂.

Numeral 60 designates an air control valve for leading a high pressureair into a wash tank 62 via a piping 61. The wash tank 62 stores thereinthe wash water for washing the interior of the compressor outlet 112.Numeral 63 designates an opening/closing valve, through which the washwater flows to be supplied into the manifold 113 via piping 64. The washwater supplied into the manifold 113 is injected from the plurality ofwash nozzles 114 into the surrounding area for washing the interior ofthe compressor outlet 112. Numeral 65 designates an opening/closingvalve and numeral 66 designates piping for supplying therethrough thewash water in a necessary quantity into the wash tank 62.

In the gas turbine compressor outlet wash system so constructed, whenthe compressor outlet 112 is to be washed, the air control valve 60 isopened and the high pressure air is led into the wash tank 62 via thepiping 61 so that the interior of the wash tank 62 is pressurized. Then,the opening/closing valve 63 is opened and the wash water is suppliedinto the manifold 113 via the piping 64. The wash water is injected fromthe wash nozzles 114 for washing the interior of the compressor outlet112.

On the other hand, as for the gas turbine operation, fuel oil is ledinto the header 13 via the flow control valve 11 and the piping 12 to bedistributed there to flow into the plurality of fuel supply pipings 14uniformly and is then supplied into the respective fuel nozzles X₂ forcombustion.

In the recent gas turbine, there is developed a dual fuel system inwhich both fuel oil and fuel gas are usable, and the fuel is changedover to gas from oil, or to oil from gas, as the case may be. In such asystem, if for example, the operation done by oil is stopped or iscontinued with the fuel being changed over to gas from oil, the fuel oilremaining in the fuel pipings and nozzles is carbonized to stick there,and there arises a fear of blockage of the fuel pipings and nozzles.Thus, an attempt is being made for providing large scale facilities bywhich the fuel pipings and nozzles are purged by air or the like. Butthese exclusive purging facilities require a large apparatus, which isare naturally undesirable from the viewpoint of cost reduction.

SUMMARY OF THE INVENTION

In view of the problems in the prior art gas turbine fuel system, it isa principal object of the present invention to provide a gas turbinefuel system comprising a fuel oil supply system and a fuel gas supplysystem so that gas turbine operation may be performed with fuel beingchanged over to either oil or gas and further comprising a controlsystem in which fuel is distributed to each fuel piping of the said fueloil supply system uniformly in an appropriate flow rate and pressure aswell as a purge system in which, while gas turbine operation is with gasfuel, residual oil in the fuel oil supply system is purged effectivelyby air or water so that the residual oil may not be carbonized.

In order to provide the gas turbine fuel system, the present inventionhas objects to provide following first to fourth systems.

First is a gas turbine fuel oil distribution control system in which acontrol valve is employed instead of a flow divider. The control valveis constructed such that differential pressure of each fuel nozzle iselevated at the initial time of gas turbine operation. Fuel oil isdistributed so as to flow into each of fuel pipings connected to fuelnozzles as uniformly as possible so that an imbalance in fuel oil flowrate caused by a head difference between each fuel nozzle is resolvedand any unusual elevation of the differential pressure at the time of ahigh fuel flow rate is prevented.

Second is a gas turbine fuel oil purge system in which, when gas turbineoperation is with fuel being changed over to gas from oil and residualoil in fuel pipings and nozzles is to be purged, the quantity of theresidual oil to be discharged into a combustor is made as small aspossible and the residual oil is purged securely to be discharged.

Third is a gas turbine fuel nozzle purging air supply system in whichcompressor outlet air of about 400° C. is cooled at a rotor cooling aircooler to an appropriate temperature to enter a pressure elevationcompressor. Some coolers are thereby made unnecessary so thatconstruction of the purging air supply system is simplified,installation space is reduced and the cost of facilities is reduced.

Fourth is a gas turbine fuel nozzle wash system in which existing gasturbine facilities may be used by being modified with a simpleconstruction so that, when fuel is changed over to gas from oil, fuelnozzles are washed by water and residual oil in the fuel nozzles iswashed out, resulting in a contribution to cost reduction of the gasturbine plant.

In order to realize the objects, the present invention provides the offollowing (1) to (5):

(1) A gas turbine fuel system comprises a fuel oil supply system forsupplying fuel oil to a plurality of fuel nozzles and a fuel gas supplysystem for supplying fuel gas to the plurality of fuel nozzles so thatgas turbine operation may be performed with fuel being changed over toeither one of oil and gas. The system further comprises a fuel oildistribution control system for controlling flow rate and pressure offuel oil in each of fuel pipings connecting to the fuel nozzles within apredetermined range by a control means provided in the fuel oil supplysystem, a fuel oil purge system provided close to the fuel nozzles inthe fuel oil supply system for purging residual oil in the fuel oilsupply system and fuel nozzles by air, a purging air supply system forsupplying air to the fuel oil purge system, and a fuel nozzle washsystem for supplying wash water to an upstream side of fuel nozzles inthe fuel oil supply system connected to the fuel nozzles.

In the invention of (1) above, the fuel oil distribution control systemcauses fuel oil to flow into the fuel oil supply system uniformly sothat any imbalance in the fuel flow rate in each of the pipings isresolved and the fuel oil purge system effectively purges the residualoil in the fuel oil supply system and fuel nozzles so that the problemof pipings being blocked by carbonization of the fuel oil is resolved.Also, the purging air supply system supplies air of an appropriatetemperature into the purge system so that air supply to the purge systemis ensured. Further, the fuel nozzle wash system purges the residual oilby injecting water so that reliability of purging the residual oil isenhanced. The air purge and water purge may be done by either of thembeing changed over to one from the other as the case may be.

(2) A gas turbine fuel oil distribution control system has a seriescontrol valve comprising a plurality of valves for controlling pressureloss in a fuel oil supply system so as to correspond to a plurality offuel nozzles. Each of the plurality of valves is controllably driven atthe same time with the same opening. A drive unit drives the seriescontrol valve. A control unit controls the drive unit, and said controlunit is inputted with a system differential pressure signal and a loadsignal of the fuel oil supply system to put out to the drive unit asignal to throttle the series control valve approximately to anintermediate opening while the system differential pressure is apredetermined low differential pressure and a signal to open the seriescontrol valve fully for a predetermined time when said systemdifferential pressure comes to a predetermined high differentialpressure.

In the gas turbine fuel oil distribution control system of the inventionof (2) above, while the series control valve is controlled in opening bythe control unit and the drive unit, the control unit is inputted with adifferential pressure signal and a load signal of the fuel oil supplysystem or the fuel nozzles to output to the drive unit a signal tothrottle the series control valve approximately to an intermediateopening while the system differential pressure is a predetermined lowdifferential pressure during the time from gas turbine ignition to ratedspeed arrival. In the high fuel flow rate area, when the systemdifferential pressure comes to a predetermined high differentialpressure, a signal to open the series control valve fully is output tothe drive unit.

Thus, the differential pressure of each of the fuel nozzles is set to ahigher differential pressure than the necessary nozzle differentialpressure by the series control valve and the gas turbine operation isperformed with the fuel oil being so controlled that imbalances in thefuel flow rate as so far occur in the low fuel flow rate area, are isreduced. Hence the prior art flow divider becomes unnecessary and thereliability of the fuel oil distribution is enhanced.

(3) A gas turbine fuel oil purge system in a gas turbine fuel oil supplysystem comprises a plurality of fuel oil supply pipings for supplyingfuel oil to a plurality of fuel nozzles via a header. A drain piping isconnected to the said plurality of fuel oil supply pipings. There isprovided a sealing connection pipe close to the fuel nozzles in each ofthe fuel oil supply pipings between the header and fuel nozzles. Apurging air supply piping supplies air to each sealing connection pipe,and each sealing connection pipe causes the air from the purging airsupply piping to flow toward the fuel nozzles as well as to flow intothe fuel oil supply pipings on the opposite side of the fuel nozzles tobe discharged from the drain piping.

In the gas turbine fuel oil purge system of the invention of (3) above,the sealing connection pipe and the purging air supply piping areprovided close to the fuel nozzles in each of the fuel oil supplypipings and air from the sealing connection pipe is injected from eachof the fuel nozzles so that the residual oil only in the very shortpiping between the sealing connection pipe and each of the fuel nozzlesis discharged into the combustor. At the same time, the combustion gasin the combustor is prevented from flowing reversely into the fuel oilsupply pipings by the air injected from the fuel nozzles, hence the airso injected has sealing function as well.

During the sealing function, the air also flows from the sealingconnection pipe into the fuel oil supply pipings on the opposite side ofthe fuel nozzles, and after flowing through the fuel oil supply pipingsand the drain piping, it is discharged outside of the system. By thisflow of air, all the residual oil in the fuel oil supply pipings isdischarged outside of the system from the drain piping. According to theinvention of (3) above, therefore, when the fuel is changed over to gasfrom oil and the residual oil in the pipings is to be purged, theresidual oil to be injected into the combustor is only the residual oilin the very short piping close to the fuel nozzles and other residualoil is discharged outside of the system from the drain piping. Hence aload change caused by burning of the residual oil is reduced.

(4) A gas turbine fuel nozzle purging air supply system in a gas turbineair system supplies air, extracted from compressor outlet air and cooledat an air cooler, to a rotor as rotor cooling air, as well as supplyingair, diverging from the air extracted from compressor outlet air andbeing elevated in pressure at a pressure elevation compressor, to beused as fuel nozzle purging air. The air cooler comprises a first coolerand a second cooler. Air cooled at the first cooler is used for therotor cooling air and air diverging from the air cooled at the firstcooler is sent to the second cooler to be cooled and then sent to thepressure elevation compressor.

In the gas turbine fuel nozzle purging air supply system of theinvention of (4) above, the air cooler comprises the first and secondcoolers and the air cooled at the first cooler is used as the rotorcooling air to be supplied for rotor cooling. Further, a portion of theair cooled at the first cooler diverges to enter the second cooler to becooled again, thus the compressor outlet air is cooled to a lowertemperature and is led into the pressure elevation compressor. When theair is compressed to a higher pressure at the pressure elevationcompressor, its temperature also is elevated, but as the air at thepressure elevation compressor inlet is sufficiently cooled to the lowertemperature at the first and second coolers, even if it is elevated intemperature, it can be used as the fuel nozzle purging air without beingcooled further.

In the prior art system, air extracted from the compressor outlet air iscooled at a separate cooler and is led into the pressure elevationcompressor to be compressed and thus to be elevated in temperature. Thisair so elevated in temperature is cooled again at another separatecooler to be adjusted to a lower temperature, which is appropriate forthe purging air. In the prior art system, therefore, separate coolersare needed and large facilities and space therefor are required. But inthe invention of (4) above, the air cooler for the rotor cooling air ismade in two units which are used for cooling the purging air as well,separate coolers are not needed, facilities are simplified and costreduction is attained.

(5) A gas turbine fuel nozzle wash system in a gas turbine wash systemcomprises a fuel oil supply system for supplying fuel oil to fuelnozzles in a combustor. A compressor wash water supply system supplieswash water to a compressor which supplies compressed air to thecombustor. A wash water tank supplies the wash water to the compressorwash water supply system. There are provided a wash water by-pass pipingand an opening/closing valve between the fuel oil supply system and thecompressor wash water supply system. When the opening/closing valve isopened, the wash water is supplied to the fuel nozzles from the washwater tank via the fuel oil supply system to be injected from the fuelnozzles so that the fuel nozzles are washable.

In the gas turbine fuel nozzle wash system of the invention of (5)above, the wash water by-pass piping and the opening/closing valve areprovided between the existing fuel oil supply system and the compressoroutlet wash system so that the wash water for compressor washing in thewash water tank is led into the fuel oil supply system. When the fuel ischanged over to gas from oil, the oil remains in the fuel nozzles and iscarbonized to stick there, which results in a fear of blockage of thefuel nozzles. Hence, when the fuel is changed over to gas, wash waterfor the compressor washing is led to the fuel nozzles via the wash waterby-pass piping and fuel oil supply system to be injected from the fuelnozzles. Thus, the fuel nozzles are washed and a fear of blockage of thenozzles is resolved. Accordingly, the existing pipings are made use ofand wash water for the compressor washing is used for nozzle washing aswell, whereby facilities cost is reduced and washing of the fuel nozzleswith a simple structure becomes possible.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an entire gas turbine fuel systemcomprising a fuel oil distribution control system, a fuel oil purgesystem, a purging air supply system and a fuel nozzle wash system of oneembodiment according to the present invention.

FIG. 2 is a diagrammatic view of the fuel oil distribution controlsystem of FIG. 1.

FIG. 3 is a view showing the relation between load transition (fuel flowrate) and system differential pressure in the fuel oil distributioncontrol system of FIG. 1.

FIG. 4 is a diagrammatic view of the fuel oil purge system of FIG. 1.

FIG. 5 is a diagrammatic view of the purging air supply system of FIG.1.

FIG. 6 is a diagrammatic view of the fuel nozzle wash system of FIG. 1.

FIG. 7 is a diagrammatic view showing one application example of thefuel nozzle wash system of FIG. 6.

FIG. 8 is a diagrammatic view showing another application example of thefuel nozzle wash system of FIG. 6.

FIG. 9 is a block diagram of an entire gas turbine fuel systemcomprising a fuel oil supply system, a fuel oil purge system, a purgingair supply system and a compressor outlet wash system in the prior art.

FIG. 10 is a diagrammatic view of the fuel oil supply system of FIG. 9.

FIG. 11 is a view showing relation between load transition (fuel flowrate) and system differential pressure in the fuel oil supply system ofFIG. 9.

FIG. 12 is a diagrammatic view of the fuel oil purge system of FIG. 9.

FIG. 13 is a diagrammatic view of the purging air supply system of FIG.9.

FIG. 14 is a diagrammatic view of the compressor outlet wash system ofFIG. 9.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Herebelow, description will be made concretely on embodiments accordingto the present invention with reference to the figures. FIG. 1 is ablock diagram of an entire gas turbine fuel system comprising therein afuel oil distribution control system, a fuel oil purge system, a purgingair supply system and a fuel nozzle wash system of one embodimentaccording to the present invention. FIG. 1 is a view of a block diagramin contrast with that in the prior art of FIG. 9.

In FIG. 1, there are provided in a combustor X a plurality of fuelnozzles X₁ and X₂, and as in the prior art, fuel nozzles X₁ are suppliedwith fuel gas from a fuel gas supply system and fuel nozzles X₂ aresupplied with fuel oil from a fuel oil supply system. Letter Adesignates a fuel oil distribution control system, which corresponds tothe fuel oil supply system G of FIG. 9. Letter B designates a fuel oilpurge system, which corresponds to the fuel oil purge system H of FIG.9, letter C designates a purging air supply system, which corresponds tothe purging air supply system J of FIG. 9, and letter D designates afuel nozzle wash system, which corresponds to the compressor outlet washsystem K of FIG. 9. Letters E, F designate selector valves,respectively, wherein in the case of air purge, the valve E is openedand the valve F is closed, and in the case of water purge, the valve Eis closed and the valve F is opened, reversely. Purging may be done byeither one of the air purge and the water purge or by a combinationthereof in which the water purge is done first and then the air purge isdone.

Description will be made below on each of the mentioned systems. FIG. 2is a diagrammatic view of the fuel oil distribution control system A ofFIG. 1, which is a view of the system in contrast with that in the priorart of FIG. 10. In FIG. 2, parts having same functions as those of theprior art shown in FIG. 10 are given the same reference letters ornumerals, with description thereof being omitted. Characteristicportions of the present invention, that is, portions 10 to 14, 20 and21, will be described in detail.

In FIG. 2, numeral 13 designates a header and numeral 14 designates aplurality of pipings connecting to the header 13. Numeral 10 designatesa series control valve, which has a series of control valves in the samenumber of pieces as that of the fuel nozzles X₂ so that each of thevalves is controlled at same time with the same opening. That is, if thenumber of the fuel nozzles X₂ is 20, for example, the series controlvalve 10 is a 20 series control valve. While illustration of thestructure of the series control valve 10 is omitted, it is for examplesuch that each of the valves is linked by a link mechanism such as acylinder and opening of the valves is controlled simultaneously.

Numeral 21 designates a drive unit, which controls opening of the seriescontrol valve 10 simultaneously, as mentioned above, and comprises ahydraulic or pneumatic cylinder or an electromotive cylinder or thelike. Numeral 20 designates a control unit, which puts out an outputsignal to the drive unit 21 so that opening of the series control valve10 may be controlled, as described later.

In the construction as mentioned above, fuel oil passes through a flowcontrol valve 11 and a piping 12 to be led into the header 13 and isthen supplied into the respective pipings 14, whose number of pieces issame as that of the fuel nozzles X₂. The respective pipings 14 connectto the respective valves of the series control valve 10, and the fueloil is supplied through the series control valve 10 and pipings 15 tothe respective fuel nozzles X₂ for combustion in the combustor X.

The series control valve 10 is controlled in valve opening via the driveunit 21 by a signal from the control unit 20, as described later, suchthat while a nozzle differential pressure is low, the opening isthrottled to an intermediate opening, and when the nozzle differentialpressure increases in a high fuel flow rate area, the valve is openedfully to make the flow resistance smaller. Thus unusual elevation of thesystem differential pressure is prevented.

FIG. 3 is a view showing the relation between load transition (fuel flowrate) and the system differential pressure in the fuel oil distributioncontrol system A of FIG. 2. In FIG. 3, while the system differentialpressure is lower than the necessary nozzle differential pressure V₁from time t₀ when the gas turbine is ignited to time t₁ when it arrivesat rated speed (no load), the series control valve 10 is throttled to anintermediate opening so that the system differential pressure iselevated higher than the necessary nozzle differential pressure V₁,which is shown by broken line in FIG. 3, as the fuel flow rateincreases.

At the time t₁, the system differential pressure arrives at differentialpressure V₂, beyond which there may occur an unusually largedifferential pressure. Then the series control valve 10 is opened fullyto make the flow resistance smaller and the system differential pressureis reduced rapidly. Then, at time t₁′, the series control valve 10 isthrottled again to an intermediate opening. After the time t₁′, thesystem differential pressure goes up again as the fuel flow rateincreases, and when it arrives at V₂, the series control valve 10 isopened fully again and thereafter the same is repeated so that controlis performed.

The system differential pressures V₁, V₂ are set in the control unit 20to be stored, and when the control unit 20 is inputted with a gasturbine load signal and a system differential pressure signal, it checksthe respective system differential pressures at times t₀, t₁ and t′ inthe load transition. When the ignition is performed at t₀, a signal tothrottle the opening of the series control valve 10 is output to thedrive unit 21 so that the opening of the series control valve 10 isthrottled to an intermediate level. When the system differentialpressure comes to V₂, a signal to open the series control valve 10 fullyis output to the drive unit 21 so that the valve is opened completely,and the same control is repeated thereafter.

According to the fuel oil distribution control system A as describedabove, opening of the series control valve 10 is controlled by thecontrol unit 20 and the drive unit 21 so that while the systemdifferential pressure is low for the time of low load after theignition, opening of the series control valve 10 is throttled to elevatethe system differential pressure. Any imbalance in the fuel flow ratedue to head differences of the fuel nozzles is resolved thereby. In thehigh fuel flow rate area, the valve is opened fully and unusualelevation of the system differential pressure is prevented thereby.Thus, a flow divider as in the prior art is not needed fuel oil flowimbalances between each of the fuel nozzles are prevented securely andthe reliability is enhanced.

Next, the fuel oil purge system B will be described with reference toFIG. 4. In FIG. 4, parts shown by reference numerals or letters 1 to 4,11 to 14, 23, X, X₁ and X₂ are the same as those in the prior art shownin FIG. 12, with description thereof being omitted. Characteristicportions of the present invention, that is parts shown by referencenumerals 30 to 33, will be described in detail.

In FIG. 4, numeral 30 designates a purging air system piping, numeral 31designates an opening/closing valve, numeral 32 designates a pluralityof sealing connection pipes and numeral 33 designates a plurality ofpipings. Each of the pipings 33 connects at its one end to each of thefuel nozzles X₂ and at its the other end to each of the sealingconnection pipes 32, and the length of each of the pipings 33 ispreferably made as short as possible. Also, each of the sealingconnection pipes 32 is a T type connection pipe which comprises portsconnecting to the pipings 14 and 33 and the purging air system piping30, respectively.

Thus, the purging air system piping 30 is connected closer to the fuelnozzles X₂, as compared with the prior art purging air system piping 26,between the header 13 and the fuel nozzles X₂. Hence residual oil in thepipings to be discharged into the combustor X is reduced, as describedlater.

In the fuel oil purge system B constructed as above, while operation isdone with fuel oil, the fuel oil passes through the flow control valve11 and the piping 12 to enter the header 13 and is distributed there toflow through the plurality of pipings 14 and the sealing connectionpipes 32 to then be supplied into the plurality of fuel nozzles X₂ viathe pipings 33, and is injected into the combustor X for combustion.

When operation is to be with the fuel changed over to gas from oil, theflow control valve 11 is closed and fuel gas is supplied instead throughthe flow control valve 1, piping 2, fuel gas distributor 3 and piping 4to enter the respective fuel nozzles X₁ to be burned in the combustor X.In this case, there remains the previous fuel oil in the piping 12,header 13, piping 14 and piping 33. If this remaining fuel oil is leftthere as it is, it is carbonized to stick there. Thus when the fuel oilhas been stopped to be changed over to fuel gas, it is necessary topurge the remaining fuel oil while operation is with the fuel gas.

In the case of purging, the opening/closing valve 31 is opened first sothat purging air 41 is led into the purging air system piping 30 to flowthrough one end each of the sealing connection pipes 32 and the piping33 to enter the fuel nozzles X₂. It is then injected into the combustorX from the fuel nozzles to be burned. At same time, the purging air 41also flows into the piping 14 through the other end each of the sealingconnection pipes 32.

Further, the opening/closing valve 24 is also opened to communicate withthe drain valve piping 23. Thus, the purging air 41 passes through thepurging air system 30, sealing connection pipes 32 and pipings 14, andfurther through the header 13, piping 12, opening/closing valve 24 anddrain valve piping 23, and is discharged outside. By the flow of thepurging air 41, the fuel oil remaining in the pipings 33 is dischargedinto the combustor X and the fuel oil remaining in the pipings 14,header 13 and piping 12 on the opposite side is discharged outside ofthe system via the drain valve piping 23.

When the purging of the residual oil is to be done while the operationis with fuel gas, as the purging air 41 from the purging air systempiping 30 flows through the one end of the sealing connection pipes 32toward the combustor X to be injected from the fuel nozzles X₂, thepurging air 41 has a sealing function to prevent reverse flow of thecombustion gas from the combustor X. In addition to this sealingfunction, the purging air 41 causes the residual oil in the pipings 14,header 13 and piping 12 on the opposite side of the sealing connectionpipes 32 to be discharged outside of the system from the drain valvepiping 23.

In the prior art case shown in FIG. 12, if the opening/closing valve 24of the drain valve piping 23 is opened during the operation, there mayarise a case that the combustion gas from the combustor X is sucked toflow reversely through the pipings 14, header 13 and piping 12 so thatthe residual oil in the pipings may burn with the high temperaturecombustion gas to damage the pipings. But in the system of the presentinvention, the purging air 41 flows from the sealing connection pipes 32toward the combustor X to be injected from the fuel nozzles X₂ so as toseal the combustion gas. Thus the shortcomings in the prior art areprevented.

According to the fuel oil purge system B as described above, theconstruction is such that the purging air system piping 30 and thesealing connection pipes 32 are connected closer to the fuel nozzles X₂between the pipings 14 and the fuel nozzles X₂. The purging air 41having the sealing function as well is injected from the fuel nozzles X₂so that the residual oil in the pipings 33 is discharged and thecombustion gas from the combustor X is prevented from flowing reverselyinto the pipings 14.

Further, the purging air 41 from the sealing connection pipes 32 flowsthrough the pipings 14, header 13 and piping 12 to be discharged fromthe drain valve piping 23 so that the residual oil in these pipings isdischarged outside of the system from the drain valve piping 23. Thuswhen the fuel is changed over to gas from oil and residual oil in thepipings is to be purged, the residual oil to be discharged into thecombustor X is only that remaining in the short pipings 33. Thus a loadchange caused by combustion of the residual oil is reduced and a largeload change is prevented.

Next, the purging air supply system C will be described with referenceto FIG. 5. In FIG. 5, parts shown by reference numerals 110, 42, 43, 48and 53 are the same as those in the prior art shown in FIG. 13, withdescription thereof being omitted. Characteristic portions of thepresent invention, that is, air coolers shown by reference numerals 50,51 and pipings thereof, as well as an accompanying simplified system,will be described in detail.

In FIG. 5, numeral 50 designates a first air cooler and numeral 51designates a second air cooler. Both of the air coolers 50, 51 arecooled by air sent from a fan 45 driven by a motor 44. In these aircoolers 50, 51, compressor outlet air is led into the first air cooler50 via the piping 42 and the air, after being cooled, is led from theoutlet of the first air cooler 50 into the gas turbine 110 as rotorcooling air via the piping 43. At same time, a portion of the air at theoutlet of the first air cooler 50 is extracted to be led into the secondair cooler 51 via piping 49.

The air cooled at the second air cooler 51 is led into a drain separator52 via a piping 46 to be removed of drainage, and is then led into thepressure elevation compressor 53 via a piping 47 to be elevated inpressure and thereby be heated to an appropriate temperature as purgingair. Thus, this air is supplied as fuel nozzle purging air via thepiping 48.

In the purging air supply system C constructed as above, the compressoroutlet air is of about 400° C. and is led into the first air cooler 50via the piping 42 to be cooled to about 200 to 250° C. by air sent fromthe fan 45. It is then supplied into the gas turbine 110 as the rotorcooling air as in the prior art.

The air cooled at the first air cooler 50 is of about 200° C. to 250° C.and a portion thereof diverges into the piping 49 to enter the secondair cooler 51. The air entering the second air cooler 51 is cooled, asin the first air cooler 50, by air from the fan 45 driven by the motor44. The air so cooled is of about 60° C. to 80° C. and is led into thedrain separator 52 via the piping 46 to be removed of drainage, and thenenters the pressure elevation compressor 53 via the piping 47 to beelevated in pressure and thereby be elevated in temperature to about100° C. to 130° C. This air of about 100° C. to 130° C. is supplied tobe used as the fuel nozzle purging air via the piping 48.

According to the purging air supply system C described above, the aircooler for obtaining the rotor cooling air is constructed in two unitsof the first air cooler 50 and the second air cooler 51. The compressoroutlet air of about 400° C. is cooled to about 200° C. to 250° C. at thefirst air cooler 50 to be used as the rotor cooling air. At the secondair cooler 51, the air so cooled to about 200° C. to 250° C. is furthercooled to about 60° C. to 80° C.

The air so cooled to about 60° C. to 80° C. is used as inlet air of thepressure elevation compressor, hence the air after being elevated inpressure is of a temperature of about 100° C. to 130° C., which isappropriate as the fuel nozzle purging air. In the prior art case asshown in FIG. 13, the air entering the pressure elevation compressor 53,which is the compressor outlet air, is of a high temperature of about400° C., and hence it is cooled as a first step to about 130° C. at thecooler 94 and is elevated in pressure at the pressure elevationcompressor 53. But this air is thereby elevated in temperature to about200° C., and hence it is cooled again at the cooler 100 for obtainingair of about 150° C.

For this purpose, there are needed the coolers 94, 100, which are largefacilities. But in the purging air supply system C of the presentinvention, the air cooler is made in two units of the first air cooler50 for obtaining the rotor cooling air and the second air cooler 51 forobtaining the fuel nozzle purging air, whereby the coolers 94, 100become unnecessary. This results in simplification of the facilities, areduction of installation space and a reduction of cost.

Finally, the fuel nozzle wash system D will be described with referenceto FIGS. 6 to 8. In FIGS. 6 to 8, the same parts as those in the priorart shown in FIG. 14 are given the same reference numerals or letters,with description thereof being omitted. Characteristic portions of thepresent invention, that is, portions shown by reference numerals 71 to75, will be described in detail.

In FIG. 6, numeral 71 designates a by-pass piping, which connects to theupstream side of the opening/closing valve 63 so that wash water fromthe wash tank 62 flows therethrough as a by-pass. Numeral 72 designatesan opening/closing valve and numeral 73 designates a header fordistributing the wash water. Numeral 74 designates a plurality of washwater supply pipings and numeral 75 designates a plurality of connectionpipes which are connected to the respective fuel supply pipings 14.

The wash water led from the wash water tank 62 into the header 73 viathe by-pass piping 71 is distributed to flow into the respective washwater supply pipings 74 and to further flow into the respective fuelsupply pipings 14 via the connection pipes 75, and then enters therespective fuel nozzles X₂.

In the fuel nozzle wash system D constructed as above, when the fuelnozzles X₂ are to be washed, the flow control valve 11 is closed, theopening/closing valve 63 is also closed, the opening/closing valve 72 isopened and the air control valve 60 is opened. Thus, high pressure airis led into the wash water tank 62 to pressurize the wash water in thetank so that the wash water is led into the header 13.

The wash water is distributed at the header 13 to flow into therespective wash water supply pipings and further to flow into therespective fuel supply pipings 14 via the connection pipes 75 and isthen injected into the combustor X from the respective fuel nozzles sothat residual oil in the fuel nozzles X₂ is washed and removed. Thewater containing the residual oil injected from the fuel nozzles X₂ isthus discharged into the combustor X and is vaporized by the hightemperature there.

FIG. 7 is a diagrammatic view showing one application example of thefuel nozzle wash system D of the present invention. In FIG. 7, what isdifferent from that shown in FIG. 6 is that the by-pass piping does notdiverge from the piping 64 of the compressor wash system, but isconnected directly to the wash water tank 62. The opening/closing valve72 is provided in this by-pass piping 67, so that the fuel nozzle washsystem is made as a separate system from the compressor wash system.Construction of the other portions of FIG. 7 is the same as that of FIG.6. In the application example shown in FIG. 7, the same function andeffects of the invention as those of the wash system shown in FIG. 6 canbe obtained.

FIG. 8 is a diagrammatic view showing another application example of thefuel nozzle wash system D of the present invention. In FIG. 8, what isdifferent from that shown in FIG. 6 is that the bypass piping isconnected to the downstream side of the opening/closing valve 63 of thecompressor wash system. In this system of FIG. 8, the compressor washsystem and the fuel nozzle wash system are operated at the same time bythe single opening/closing valve 63, wherein the opening/closing valve72 shown in FIGS. 6 and 7 is eliminated. Construction of the otherportions of FIG. 8 is the same as that of FIGS. 6 and 7. In theapplication example shown in FIG. 8, the same function and effects ofthe invention as those of the wash system shown in FIGS. 6 and 7 can beobtained.

According to the fuel nozzle wash systems D shown in FIGS. 6 and 7, theconstruction is such that there are provided the by-pass pipings 71, 67for conducting therethrough the wash water from the wash water tank 62of the compressor outlet wash system in a by-pass. The wash water flowsthrough the header 73, wash water supply pipings 74 and connection pipes75 to the respective fuel supply pipings 14, and is then supplied intothe fuel nozzles X₂ for washing the residual oil in the fuel nozzles X₂.Also, according to the fuel nozzle wash system D shown in FIG. 8, theconstruction is such that the piping 64 of the compressor outlet washsystem and the piping 68 of the fuel nozzle wash system are connected tothe wash water tank 62 via the single opening/closing valve 63. Thus, bythese constructions, washing of the fuel nozzles X₂ can be done by thewash water from the wash water tank 62 of the compressor outlet washsystem, and no exclusive wash apparatus of the fuel nozzles X₂ isneeded. Hence the wash system can be made in a simple piping structure,which contributes to cost reduction of the gas turbine plant.

It is understood that the invention is not limited to the particularconstruction and arrangement herein illustrated and described butembraces such modified forms thereof as come within the scope of theappended claims.

What is claimed is:
 1. A gas turbine fuel system comprising a fuel oilsupply system for supplying fuel oil to a plurality of fuel nozzles anda fuel gas supply system for supplying fuel gas to said plurality offuel nozzles so that gas turbine operation may be done with fuel beingchanged over to either one of oil and gas, further comprising a fuel oildistribution control system for controlling flow rate and pressure offuel oil in each of fuel pipings connecting to said fuel nozzles withina predetermined range by a control means provided in said fuel oilsupply systems; a fuel oil purge system provided upstream to said fuelnozzles in said fuel oil supply system for purging residual oil in saidfuel oil supply system and fuel nozzles by air; a purging air supplysystem for supplying air to said fuel oil purge system; and a fuelnozzle wash system for supplying wash water to upstream side of saidfuel nozzles in said fuel oil supply system connected to said fuelnozzles.